Decision Tables and Decision Trees

ByBhumika shah

Decision Table

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Decisiontablesprovideawaytoexamine,describe, anddocument decisions using a table.

Theyareusedto

Describe the conditions

Identifypossible decision alternatives

Indicate actions should be performed, and

Describe actions

Decision Table

A matrix representation of the logic of a decision.

Specifies the possible conditionsand the resulting actions.

Best used for complicated decision logic.

Consists of three parts Condition stubs

Lists condition relevant to decision Action stubsActions that result from a given set of conditions Rules

Specify which actions are to be followed for a given set of conditions.

Decision Table Structure

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Decision table for payroll system

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Decision Table Types

Major2 types of Decision Table

Limited Entry Decision Table Yesor Noanswers to condition and action statements.

Extended Entry Decision Table Descriptive orin quantified form

Mixed Entry Decision Table Bothfixedandvariable entries

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Advantages of Decision Table

Managers can be relieved from decision making for routine matters.

Complex decisions rules may be structured.

Consistency in decision making.

Communication between the manager and system analyst becomes easier.

A method of documentation that can be easily prepared, changed and updated

Summarized and standardized format, hence easier to use.

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Disadvantages of Decision Table

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Anadditional burden.

Doesnotdepict the flow by logic of asolution to a given problem.

Noteasy to translate it into source program.

Decision Trees

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Decision trees are used when complex branching occurs inastructured decision process

Trees are also useful when it is essential to keepa string ofdecisions ina particular sequence

Drawing Decision Trees

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First,identifyall conditions and actionsand the order and timingof these (if they are critical).

Second, begin building thetree from left to right while makingsureyouarecomplete in listing all possible alternatives before

moving over to the right.

Decision Trees

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Decision Trees

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Decision Tree Advantages

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Three advantages are:

Theorder of checkingconditions and executing actions isimmediately noticeable.

Second, conditions and actions of decision trees are foundon some branches but not on others.

Third,decision trees are more readily understood by othersin theorganization.

Selectinga Structured DecisionAnalysis Technique

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Use these guidelines:

Use decision tables when complex combination of conditions, actions, and rules are found or you require a method that effectively avoids impossible situations,redundancies, and contradictions.

Use decision trees when the sequence of conditions and action is critical or when not every condition is relevant to every action (the branches are different)

Comparing Tools

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Criteria Decision Tables Decision Trees

Determining ConditionsandActions

Transforming

Second Best Best

Conditions and Actions Second Best BestintoSequence

Checking ConsistencyandCompleteness

Best Best

Thank You